1. Field of the Invention
The present invention relates to an imaging apparatus using a flash apparatus, a camera system having an imaging apparatus and a flash apparatus, and a controlling method therefor.
2. Description of the Related Art
There are known camera systems including a flash apparatus and an imaging apparatus, in which, when the photographing (strobe photographing) is executed by using the flash apparatus, pre-light emission is executed before main light emission to be performed photometry by a photometry sensor, or the like, and an light amount for the main light emission is controlled based on the result of the photometry. In such camera systems, the photographing is executed in a live view state in which an image received by an imaging element is displayed on a display apparatus in real time.
When the strobe photographing is executed in the live view state, there exists a method for performing photometry of the pre-light emission with the imaging element. There also exists a method for performing photometry of the pre-light emission, after returning a main mirror from a photographing state to a monitoring state, by using a photometry sensor for performing photometry of light passing through a lens with wide dynamic range. Hereinafter, each operation for the above methods will be described. Here, the photographing state means such a state that to cause the imaging element to receive light of an object image, the main mirror is evacuated from a light path lying between a photographing lens and the imaging element. The monitoring state means such a state that, to cause the photometry sensor provided separately from the imaging element to receive light of the object image, the main mirror has entered the light path. In the photographing state, while the object image can not be confirmed with an optical finder, such a setting becomes available that the object image is displayed in real time on an image display unit such as a backside monitor of the camera system. On the other hand, in the monitoring state, while the object image can not be displayed in real time on the image display unit, the object image can be confirmed with the optical finder.
FIG. 6 is a timing chart illustrating a conventional strobe photographing operation in the live view state when using the method for performing photometry of the pre-light emission with the imaging element. This timing chart illustrates a waveform (light emission waveform) 60A indicating intensity of the pre-light emission by the flash apparatus, a control signal 60B for controlling to accumulate a charge of the imaging element (hereinafter, simply referred to as “accumulating”) and to read the charge as voltage (hereinafter, simply referred to as “reading”), and an output (output of the imaging element) 60C of the voltage of the imaging element. Here, the output 60C of the imaging element indicates either an output of the voltage of a specific area in the imaging element or an average output of the voltage of the imaging element. Here, the control signal 60B is schematically illustrated, an H level thereof indicates the accumulating, and an L level thereof indicates the reading. FIG. 6 also illustrates a saturation value of the output 60C of the imaging element, that is, a maximum output 60C_MAX.
In this camera system, in the live view state, the reading from the imaging element is periodically executed. Thus, the control signal 60B alternately turns the H level and the L level (T1 to T2 to T3, T3 to T4 to T5 in FIG. 6). Next, the pre-light emission is executed (T5 to T6 in FIG. 6). In this case, when a distance from the camera system to the object is short, or the rate of reflection of the object is high, the output of the imaging element may be saturated (6, T6 to T7 in FIG. 6). In such a case, an amount of the pre-light emission is decreased, and the pre-light emission is executed again (T5 to T9 in FIG. 6).
It is assumed that the photometry for the pre-light emission is appropriately completed when a level of the output 60C of the imaging element for the pre-light emission (a photometric value for the pre-light emission) is not saturated. Based on this photometric value for the pre-light emission, the amount of the main light-emission for the main exposure (image recording) is calculated, and the main light-emission of the flash apparatus is executed while the accumulating of the imaging element is being executed (T11 to T12 in FIG. 6).
FIG. 7 is a timing chart illustrating a conventional strobe photographing operation in the live view state when using the method for performing photometry of the pre-light emission, after returning the main mirror from the photographing state to the monitoring state, by using the photometry sensor for performing photometry of the light passing through a lens with wide dynamic range.
This timing chart illustrates a waveform (light emission waveform) 70A indicating the intensity of the pre-light emission by the flash apparatus, a control signal 70B for controlling the accumulating and the reading from the imaging element, and an output (output of the imaging element) 70C of the voltage of the imaging element. Here, the output 70C of the imaging element indicates either an output of the voltage of a specific area in the imaging element or an average output of the voltage of the imaging element. Here, the control signal 70B is schematically illustrated, the H level thereof indicates the accumulating, and the L level thereof indicates the reading. FIG. 7 also illustrates a saturation value of the output 70C of the imaging element, that is, a maximum output 70C_MAX.
In addition, this timing chart illustrates, in the monitoring state of the main mirror, a sensor control signal 70E for controlling the accumulating and the reading by using the photometry sensor for performing photometry of the light passing through the lens, and an output (output of the photometry sensor) 70F of the voltage of the photometry sensor. Here, the H level of the sensor control signal 70E indicates the accumulating, and the L level indicates the reading. FIG. 7 also illustrates the saturation value of the output 70F of the photometry sensor, that is, a maximum output 70F_MAX of the photometry sensor. Meanwhile, in a photometry sensor, a value compressed by LOG (logarithm) is generally outputted to obtain a wide dynamic range.
In this camera system, in the live view state, the reading from the imaging element is periodically executed (T1 to T2 to T3, T3 to T4 to T5 in FIG. 7). When the photographing (strobe photographing) is executed by using the flash apparatus, the main mirror is changed from the photographing state to the monitoring state (T5 to T6 in FIG. 7). To perform photometry of ambient light before the light emission by the flash apparatus, the photometry sensor executes the accumulating (T6 to T7 in FIG. 7). Next, the output of the photometry sensor is read (T7 to T8 in FIG. 7).
To perform photometry of the light radiated by the pre-light emission of the flash apparatus, the pre-light emission is executed by the flash apparatus during the accumulating is executed by the photometry sensor (T9 to T10 in FIG. 7). Next, the output of the photometry sensor is read (T10 to T11 in FIG. 7).
From the ambient light before the pre-light emission and the photometric value during the pre-light emission, the amount of the main light emission of the flash apparatus in the main exposure is calculated while changing the main mirror to the photographing state (T11 to T12 in FIG. 7). In the accumulating of the imaging element, the flash apparatus executes the main light emission (T12 to T13 in FIG. 7).
As a camera system which uses the photometry sensor with wide dynamic range for performing photometry of the pre-light emission, there is a known imaging apparatus which is described in Japanese Laid-Open Patent Publication (Kokai) No. 2007-020125. In this imaging apparatus, when the flash imaging is executed from an electronic monitoring state, a shutter is caused to close before the flash imaging, and an amount of the light emission of a flash unit is set based on an output from a receiving element receiving reflected light from the shutter.
However, the following problems have been included in the above camera system. In the above method for performing photometry of the pre-light emission with the imaging element, the imaging element outputs in a format without log compression, so that the dynamic range is narrow. When an amount of received light in the pre-light emission becomes out of the dynamic range of the imaging element, the amount of the pre-light emission is changed and the photometry is executed again. Thus, since the pre-light emission is often required more than once, a time lag (release time lag) until an imaging operation is started after a release button is pressed has not be stabilized, or the time lag needs to be set a large value for stability thereof.
In the method for performing photometry of the pre-light emission, after returning the main mirror from the photographing state to the monitoring state, by using the photometry sensor for performing photometry of the light passing through a lens with wide dynamic range, the following problems have been included. That is, the method requires the following times, so that the time lag becomes large: a time for causing the main mirror to move from the photographing state to the monitoring state (T5 to T6 in FIG. 7); and a time for causing the main mirror to return from the monitoring state to the photographing state (T11 to T12 in FIG. 7).